The ionic model – IB DP Chemistry- Study Notes | IITian Academy

The ionic model - IB DP Chemistry- Study Notes - New Syllabus 2025

The ionic model  – IB DP Chemistry- Study Notes

IITian Academy excellent Introduction to the Particulate Nature of Matter – Study Notes and effective strategies will help you prepare for your IB DP Chemistry 2025 exam.

IB DP Chemistry Study Notes – All Topics

S2.1.1 – Ions

Ions:

  • Charged particle that forms when an atom gains or loses electrons
  • Positively charged Ions are called Cations.
  • These lose electrons
  • Negatively charged Ions are called Anions.
  • These gain electrons.
  • Charge is equal to the amount of electrons gained or lost

Cations from Group 1 , 2, and 3:

1. Group 1

  • 1. Have one valence electron, so they tend to lose one electron and form 1+ ions.

2. Group 2

  • Have two valence electrons, so they tend to lose two electrons and form 2+ ions.

3. Group 13 or 3

  •  Have three valence electrons, so they tend to lose three electrons and form 3+ ions.

NOTICE THAT FOR IONS, THE CHARGE IS LISTED AFTER THE NUMBER (Ca2+, Al3+).

OXIDATION STATES ARE LISTED WITH THE CHARGE BEFORE THE NUMBER (+2, +3).

4. Group 4

  • Tend to not lose or gain electrons due to the amount of energy involved so they do not normally form ionic bonds.

Anions from Group 5 , 6, and 7:

1. Group 15 or 5

  •  Have five valence electrons, so they tend to gain 3 electrons and form 3- ions.

2. Group 16 or 6

  •  Have six valence electrons, so they tend to gain 2 electrons and form 2- ions.

3. Group 17 or 7

  •  Have seven valence electrons, so they tend gain 1 electron to form 1- ions.

ELECTRONS ARE GAINED OR LOST TO HAVE 8 ELECTRONS IN THEIR OUTER SHELL.

4. The names of anions ends with “ide”

Predicting Ionic Charge based on Electron Configuration:

  •   Atoms lose or gain electron to attain noble gas configuration
  •   Sodium atom Na → $1s^{2}2s^{2}2p^{6}, 3s^{1} or [Ne]3s^{1}$
  •    Sodium ion $Na^{1+} →  1s^{2}2s^{2}2p^{6} or [Ne]$
  •   Chlorine atom $Cl → 1s^{2}2s^{2}2p^{6}3s^{2}3p^{5} or [Ne] 3s^{2}3p^{5}$
  •   Chloride ion $Cl^{1-} →  1s^{2}2s^{2}2p^{6}3s^{2}3p^{6} or [Ar]$

Transition Elements:

  • Transition elements have electron configurations that allow them to lose different amounts of electrons from their d-sublevels.
  • They can form more than one stable ion.
  • The ions can be distinguished by color.
  • Here are some common examples:
  • Lead forms $Pb^{4+}$ and $Pb^{2+}$
  • Iron forms $Fe^{2+}$ → Colorless
  • $Fe^{3+}$→ Brown

S2.1.2 – Ionic Bonds

Ionic Bond:

  •  Refers to the electrostatic attraction experienced between the electric charges of a cation or anion.
  • These ARE POLAR

Ionic Character:

Two ways to predict:

  • Position on the Periodic Table
  • Electronegativity differences

1.  Position on the Periodic Table

  • Metals on the left side of the zigzag line tend to lose electrons
  • Non-metals on the right side of the zigzag line tend to gain electrons.
  • The highest tendency to form ionic compounds will be between elements on the bottom left with elements on the top right.

2. Electronegativity

  • 1. Differences greater than 1.8 are ionic.
  • 2. Electronegativity is given in the data booklet

Polyatomic Ions:

  • Ions that contain more than all atoms

Naming Ionic Compounds:

  • The name of the cation is given first and is followed by the anion
  • Cations adopt the name of the parent atom and the name remains unchanged
  • Monatomic anions adopt the first part of the name of the parent atom, followed by the suffix “-ide”. If the anion is polyatomic its name remains unchanged.
  • The name of the compound does not reflect the number of ions in the formula

S2.1.3 – Lattice and Properties of Ionic Compounds

Lattice Structure:

  • The ions in ionic compounds surround themselves with ions of the opposite charge.
  •  Because of this, ionic compounds have three-dimensional crystalline structures known as ionic lattices.

Lattice Enthalpy:

  •  Energy needed to break lattice bonds
  •  Smaller the ion → greater charge → higher lattice enthalpy
  •   For example: NaCl or KCl
  •  NaCl > KCl because Na has smaller radius
  • Higher lattice enthalpy of NaCl
  • Smaller ions size → more lattice enthalpy·         The formula unit is the smallest particle of an ionic compound.

Physical Properties of Ionic Compounds:

  •  High melting/boiling points.
  •  Strong electrostatic attraction between ions.
  • Large amount of energy is needed to break the bond.
  •  Compounds are hard and brittle.
  •  High charge → smaller ion → greater melting point.
  •  High lattice enthalpy → High melting/boiling point
  •  NOT malleable or ductile.

Volatility:

  • The tendency of a substance to vaporize.
  •  Vaporize: the ability for something to be converted into vapor
  •  Ionic compounds have very low volatility
  •  Due to strong electrostatic forces of attraction between oppositely charged ions.

Solubility:        →         →         →             

  •   Ability of solid to dissolve in a liquid to become a solution.
  •  Solubility trends are based on the similarity of the chemical nature of the solute and the solvent.
  •  Polar compounds dissolve in polar solvents.
  •  Nonpolar compounds dissolve in nonpolar solvents

Electrical Conductivity:

  • Ability to conduct electricity.
  •  Requires free moving ions
  •  Molten and dissolved Ionic compounds CAN CONDUCT ELECTRICITY
  •  Solid ionic compounds do not conduct electricity
  •  Because the ions are locked into place and are not free to move about.

Brittleness:

  •  The crystal will shatter when force is applied.
  •  Ionic compounds tend to be brittle because:
  •  Ions of like charge can be next to each other in the lattice structure
  •  The repulsive charges cause the structure to split easily
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